This invention relates to an induction system for an internal combustion engine and more particularly to an induction system for an internal combustion engine that improves the performance throughout the entire speed and load ranges of the engine.
It has been well known that the power output of an internal combustion engine and its performance is dependent upon the induction system of the engine. Conventionally, engine induction systems are tuned so as to represent a compromise between high speed performance and low speed performance. Recently, however, it has been proposed to employ a form of variable induction system wherein the induction system can be tuned so as to improve the performance through a wider range of the engine's running condition. One way in which this is done is to provide a pair of plenum chambers, each of which serves the engine induction system through respective manifold runners and the plenum chambers and runners are tuned so as to serve different running conditions of the engine.
With such arrangements, it has been the common practice to provide throttle valves between one of the plenum chambers and its induction passages and also to have a common portion for the induction passages of both systems. Such arrangements reduce the complexity and cost of the engine. With this type of arrangement, it has heretofore been the practice to provide the atmospheric air inlet and throttle valve for the engine at the plenum chamber that serves the low speed and midrange running conditions of the engine. The plenum chamber for the high speed running receives its atmospheric air through the same inlet and through the manifold induction passages.
This has some disadvantages. Primarily, the fact that the atmospheric air for the high speed plenum chamber must flow from the low speed plenum chamber, there is some flow resistance and some reduction of maximum power output. Also, the positioning of the throttle valves in certain prior art arrangements is such that the throttle valves restrict the flow of air through the induction system and, accordingly, reduce the power output of the engine.
It is, therefore, a principal object of this invention to provide an improved intake system for an internal combustion engine.
It is a further object of this invention to provide an induction system for an internal combustion engine that can improve the performance throughout the entire engine load and speed ranges and which will be relatively simple in construction and cost.
It is a further object of this invention to provide a variable induction system for an internal combustion engine wherein maximum power can be achieved without any losses in low range performance.